When k channels using the same frequency resource are allocated in a wireless network consisting of N cells, a frequency reuse factor (FRF) may be defined to be k/N.
In order to mitigate inter-cell interference, when constituting the wireless network, a cellular system is changing from a scheme of not allocating the same frequency to neighboring cells (generally, FRF< 1/7) to a scheme of allocating the same frequency to the neighboring cells (FRF=1). Also, an inter-cell interference mitigating algorithm is changing from a scheme that is embodied at a receiver side to a scheme that is embodied at a transmitter side, that is, to a fractional frequency reuse (FFR) scheme or a network multiple input multiple output (MIMO) scheme.
The FFR scheme may obtain a large FRF value to thereby enhance spectrum use efficiency. The FFR scheme may be classified into a hard FFR scheme and a soft FFR scheme.
The hard FFR scheme does not allow neighboring cells to use the same frequency in a cell boundary region in order to mitigate inter-cell interference in a network. Particularly, in an orthogonal frequency division multiple access (OFDMA) system, the neighboring cells do not allocate the same subcarriers to terminals, located in the cell boundary region, due to cooperation among the neighboring cells. Unlike the hard FFR scheme, the soft FFR scheme allows the neighboring cells to use specific subcarriers, but may mitigate the inter-cell interference in the network by adjusting transmission power of the specific subcarriers to mitigate the inter-cell interference through cooperation of the neighboring cells.
In the network MIMO scheme, antennas installed at base stations of the neighboring cells may cooperatively perform MIMO transmission/reception to thereby mitigate the inter-cell interference or to enhance system performance.